U0106 Lost Communication with Glow Plug Control Module
The U0106 code indicates that the engine control module (ECM/PCM) has lost communication over the CAN bus with the Glow Plug Control Module (GPCM). This module manages the timing and intensity of glow plug heating in diesel engines, which is critical for cold starts and reducing emissions during warm-up. Loss of communication can stem from CAN bus wiring faults, power supply issues to the GPCM, or internal module failure.
1. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.
2. Most Common Causes
- Open or shorted CAN bus wiring (short to ground or battery)
- Corroded, oxidized, or damaged GPCM connector pins
- Internal failure of the Glow Plug Control Module (GPCM)
- Power supply problem to the GPCM (blown fuse, faulty relay, voltage drop)
- Faulty ECM/PCM preventing communication
- Abnormal resistance in the CAN bus termination circuit
3. Symptoms You Will Notice
- Check Engine Light illuminated
- Hard starting in cold weather or extended cranking
- Rough idle or misfire during warm-up
- Increased exhaust smoke on cold start
- Glow plug warning light on the dashboard
4. Step-by-Step Diagnosis
Scan for other related CAN bus communication codes
Visually inspect the GPCM connector and wiring for damage, corrosion, or loose pins
Check the GPCM power supply fuse and relay, and measure voltage at the module
Test CAN bus wiring for continuity, shorts, and proper termination resistance (60 ohms)
If wiring and power are OK, attempt to communicate with the GPCM via scan tool; if no response, suspect a failed GPCM
As a last resort, check the ECM/PCM for internal faults
5. Frequently Asked Questions
Is it safe to drive?▼
You can drive short distances in mild weather, but cold starts may be difficult and emissions will increase. It's best to repair promptly to avoid being stranded.
How much does it cost to fix?▼
Diagnosis typically costs $100-$150. Repair costs vary: a new GPCM ranges from $200-$600 plus labor, while wiring repairs are usually $100-$300.